Generally used in fluid control devices, for example, for manufacturing semiconductors are pipe joints which comprise a pair of tubular joint members, an annular gasket interposed between the abutting end faces of the two joint members and screw means for joining the two joint members. With such pipe joints, the tubular joint members and the gasket are usually made of a metal, such as SUS316L or like stainless steel.
While various fluids are passed through conventional pipe joints of stainless steel in the process for manufacturing semiconductors, these fluids include those having properties to readily corrode metals, such as acidic ammonium fluoride, and it is desired to improve the joint. Although it appears feasible to make the members of the pipe joint from PFA or like synthetic resin, synthetic resin members undergo a greater alteration in shape (e.g. stress relaxation or cold flow) with time than metal members, and the specific pressure occurring between the members at the abutting portions gradually decreases, possibly resulting in leakage of the fluid.
An object of the present invention is to provide a pipe joint wherein the portions to be brought into contact with a fluid are made of a synthetic resin and which retains the ability to prevent fluid leaks despite the lapse of time.